Transport engineering is one of the most technically developed and ever growing industries. One of the industry development trends deals with replacing combustion engines powering most conventional vehicles with alternative drives. Currently attention is focused on hybrid electric vehicles and electric vehicles driven by eco-friendly electric motors and motor wheels.
Hybrid electric vehicles and electric vehicles driven by electric motor wheels have a number of advantages over conventional vehicles using combustion engines. Such advantages include fewer complex and heavy transmission gears between the motor and the wheel (clutch, transmission, drive shafts and differentials), improved dynamics, maneuverability, fuel efficiency, and road safety. However, conventional motor wheels possess a number of significant drawbacks, the most important of which is high unsprung weight of motor wheel. Furthermore, small high-speed electric motors comprised in motor wheels require a reduction gear which transfers rotational torque transmitted to the wheel by the electric machine, wherein said gear has to be small due to limited space within the motor wheel. Therefore, conventional hybrid electric vehicles, such as cars, electric cars and buses provided with motor wheels, have high unsprung weight, resulting in a less comfortable drive in such vehicle due to vibrations being transmitted to the vehicle body, worse handling, and significant increase in car suspension wear when driving at high speeds or on roads with low surface quality. Further, one of the most significant disadvantages of the conventional motor wheels is structural complexity, and therefore, a large number of parts comprised in the motor wheel, which leads to an excessive increase in motor wheel costs and significantly limits production rates.
RU2334626 (B60K7/00) discloses a motor wheel for an electric vehicle, the motor wheel comprising an electric motor comprising an electric motor stator fixedly mounted on load-bearing suspension members of the vehicle wheel and an electric motor rotor. The electric motor rotor is arranged on the vehicle wheel hub, wherein the active rotor member, with a “squirrel cage” consisting of two steel rings connected to each other by means of steel pins arranged therein, is made of a light-alloy material, comprises a ring-shaped insert with a flange having openings therein, and is affixed to the hub by means of screws. The gap between the ring-shaped insert and the wheel hub is filled with a polymer adhesive. The design of the prior art motor wheel is relatively simple due to combining the rotor with the wheel hub, and the weight of the wheel is lower due to a decrease in active rotor member weight. However, the disadvantage of the prior art motor wheel is a lack of electric motor springing; thus the electric motor weight is a component of unsprung weight of the electric vehicle. The lack of electric motor springing leads to an increased risk of rotor deformation during dynamic wheel vibrations, which breaks the uniformity of the gap between the rotor and the stator and can lead to rotor rotation jamming.
WO2014013084 (B60K7/00, B60K17/04) discloses a motorized hub comprising reduction means, the hub comprising an electric traction machine with an external stator connected to the hub carrier and an internal rotor. The prior art motorized hub further includes reduction means comprising three reduction stages and coupling/uncoupling means for coupling with the reduction means and for uncoupling therefrom. A significant disadvantage of the prior art motorized hub is a significant weight of the structure, and, therefore, high unsprung weight of the vehicle, which leads to a significantly less comfortable drive and a decrease in dynamic stability of the vehicle. Further disadvantages include high load on parts of the motorized hub in operation.
US20060144626 (B60K1/00, B60K7/00, F16H57/02) describe an in-wheel motor, comprising a wheel, an electric motor, a reducer (planetary reduction gear) for transmitting rotation from the electric motor to the wheel, a damper mechanism connecting the outer part of the electric motor case with the knuckle in such manner that the electric motor case can vibrate in vertical direction. The disadvantages of the solution include structural complexity, high manufacturing costs and high weight due to, in particular, the required significant strengthening of the electric vehicle body.